Now all my bookmarks, history, passwords and the like will be stored on a centralized server? The decentralization, especially in the wake of the NSA/GCHQ revelations, was one of its main advantages. Sigh. I may well have to turn Firefox sync off then.
They were already stored in a centralized server. They were just encrypted, and they'll continue to be.
I'm still a little unsure if this new system is less secure, however.